The Chloroplast Import Receptor Toc90 Partially Restores the Accumulation of Toc159 Client Proteins in the Arabidopsis thaliana ppi2 Mutant

Successful import of hundreds of nucleus-encoded proteins is essential for chloroplast biogenesis. The import of cytosolic precursor proteins relies on the Toc- (translocon at the outer chloroplast membrane) and Tic- (translocon at the inner chloroplast membrane) complexes. In Arabidopsis thaliana,precursor recognition is mainly mediated by outer membrane receptors belonging to two gene families: Toc34/33 and Toc159/132/120/90. The role in import and precursor selectivity of these receptors has been intensively studied,but the function of Toc90 still remains unclear. Here,we report the ability of Toc90 to support the import of Toc159 client proteins. We show that the overexpression of Toc90 partially complements the albino knockout of Toc159 and restores photoautotrophic growth. Several lines of evidence including proteome profiling demonstrate the import and accumulation of proteins essential for chloroplast biogenesis and functionality.     

Feedback Specificity, Learning Opportunities, and Learning.

Although increasing feedback specificity is generally beneficial for immediate performance, it can undermine certain aspects of the learning needed for later, more independent performance. The results of the present transfer experiment demonstrate that the effects of increasing feedback specificity on learning depended on what was to be learned, and these effects were partially mediated through the opportunities to learn how to respond to different task conditions during practice. More specific feedback was beneficial for learning how to respond to good performance and detrimental for learning how to respond to poor performance. The former relationship was partially mediated by feedback specificity's effect on learning opportunities during practice. The results have implications for designing feedback interventions and training to maximize the learning of various aspects of a task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Especial Skills: Their Emergence With Massive Amounts of Practice.

Differing viewpoints concerning the specificity and generality of motor skill representations in memory were compared by contrasting versions of a skill having either extensive or minimal specific practice. In Experiments 1 and 2, skilled basketball players more accurately performed set shots at the foul line than would be predicted on the basis of the performance at the nearby locations, suggesting considerable specificity at this distance. This effect was replicated even when the lines on the court were obscured (in Experiment 2). However, the effect was absent when jump shots were executed in Experiment 3. The authors argue that massive levels of practice at 1 particular member of a class of actions produce specific effects that allow this skill to stand out from the other members of the class, giving it the status of an especial skill. Various theoretical views are proposed to account for the development of these skills. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Site-directed mutagenesis of glyceraldehyde-3-phosphate dehydrogenase reveals the role of residue Ser148

A mutant of Bacillus stearothermophilus D-glyceraldehyde-3-phosphatedehydrogenase, Ser¹⁴⁸ – Ala, was produced byoligonucleotide-directedmutagenesis. The study of the catalytic properties of this mutanthas shown that this mutation significantly affects the Michaelisconstant of inorganic phosphate and to a lesser extent thatof 1,3-diphosphoglycerate and D-glyceraldehyde-3-phosphate.This result is consistent with model-building studies whichshow that, for the phosphorylation step of catalysis, inorganicphosphate must bind to the anion recognition site designatedP_i with the C(3) phosphate of the acyl-enzyme intermediate inthe alternative anion site P_s. Studies of the enantiomeric specificityusing D- and L-glyceraldehyde as substrates show that the hydroxylgroup of Ser¹⁴⁸, combined with the presence of the C(3) phosphateof the substrate, enhances stereospecificity as well as catalysis.However, the stereospecific effect cannot be a consequence ofthe direct interaction of Ser¹⁴⁸ with the C(2)-hydroxyl of thesubstrate. The changed K_m for glyceraldehyde-3-phosphate suggeststhat the initial step of hemithioacetal formation may take placewith its C(3) phosphate bound in the P_i site. This supportsthe molecular mechanism proposed by Moody (1984). Therefore,catalysis could be enhanced through interactions of the serinehydroxyl group not only with inorganic phosphate but also withthe C(3) phosphate of glyceraldehyde-3-phosphate.     

Peculiar properties of lipase fromCandida parapsilosis (Ashford) langeron and talice

A newCandida parapsilosis lipase was isolated and studied. This enzyme was purified by hydrophobic chromatography on a phenyl-sepharose CL4B column followed by gel permeation on a Sephacryl S300 HR column. It was a 160 kg·mol⁻¹ molecular-weight oligomeric enzyme. Optimal activity was obtained at 45°C and pH 6.5. The lipase activity toward various acylglycerols and esters was studied. The hydrolysis rate was greater for secondary acylesters than for primary acylesters. This lipase showed a high specificity for long-chain fatty acids and particularly for polyunsaturated fatty acids. This enzyme was able to catalyze the synthesis of various oleoylesters in aqueous medium.     

Representational specificity of within-category phonetic variation in the long-term mental lexicon.

This study examines the potential encoding in long-term memory of subphonemic, within-category variation in voice onset time (VOT) and the degree to which this encoding of subtle variation is mediated by lexical competition. In 4 long-term repetition-priming experiments, magnitude of priming was examined as a function of variation in VOT in words with voiced counterparts (cape-gape) and without (cow-*gow) and words whose counterparts were high frequency (pest-best) or low frequency (pile-bile). The results showed that within-category variation was indeed encoded in memory and could have demonstrable effects on priming. However, there were also robust effects of prototypical representations on priming. Encoding of within-category variation was also affected by the presence of lexical counterparts and by the frequency of counterparts. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

3组常见马源性成分鉴定引物特异性和灵敏度比较

比较筛选基于聚合酶链式反应(polymerase chain reaction, PCR)技术的马源性成分鉴定方法中高灵敏度和特异性引物。方法 选取来自国标法、专利和文献报道的3组马源性成分鉴定引物, 比较其灵敏度和特异性, 筛选高灵敏度和特异性引物。结果 3组引物的灵敏度和特异性存在差异, 以线粒体DNA为靶标的Ⅱ组马源性成分鉴定引物的特异性和灵敏度优于分别以线粒体和核基因组DNA为靶标的马驴通用鉴定引物, 检出最低限度均满足检测需求。结论 通过比较马源性成分鉴定的3组PCR引物, 以线粒体DNA为靶标的Ⅱ组马源性成分特异性鉴定引物可作为马成分鉴定的首选, 线粒体和核基因组靶标联合可提高马成分鉴定的准确性并可用于杂交种鉴定, 为马源性成分及产制品鉴定提供了一定基础。     

Mapping the Limits of Substrate Specificity of the Adenylation Domain of TycA

The limits and potential of substrate promiscuity of the adenylation domain of tyrocidine synthetase 1 were systematically explored. Substrate acceptance is governed by hydrophobic effects (as shown by the correlation of k_cat/K_M and side‐chain log P), shape complementarity and steric exclusion. The quantification of these factors provides ground rules for understanding and possibly evolving substrate specificity in this class of enzymes.